Recently, considerable interest has been shown within the detergents industry as well as among consumers and sale centers in concentrated to highly concentrated detergent powder compositions having a relatively high bulk density of above 600 g/l, preferably at least 610 g/l. The term "detergent powder compositions" used herein refers to particulate detergent compositions consisting of granules or particles or mixtures thereof, of a size which, as a whole, will have the appearance of a powdered composition. Currently, highly concentrated detergent powder compositions having a bulk density of at least 650 g/l to even above 750 g/l have been commercialized.
The trends, begun in the last year or two, are coming along in the detergents industry, with environmentalism and concentrated detergents going hand in hand.
The advantages of concentrated detergents powder compositions are evident, of which the following are particularly worth mentioning:
(i) smaller containers or packs provide easier handling to the consumer;
(ii) savings in storage and transport costs;
(iii) smaller packs create shelf space for stacking more pack per unit space;
(iv) less packing material will result in less waste to the environment.
For the concentration of powdered detergents and to achieve smaller packs, in principle the following possibilities exist:
using more active components;
avoiding activity losses during the manufacture and storage;
minimizing the amount of or avoiding all non-functional ingredients used in the manufacturing process;
minimizing the amount of air and moisture in the product as well as in the packet.
Non-functional ingredients are ingredients not really essential to the washing performance, particularly sodium sulphate. Minimizing the amount of air in the product and packet can be achieved by densifying and shaping the particles so as to reduce the specific volume of the product, i.e. increasing the bulk density.
Foremost as essential ingredients in the formulation of modern heavy duty detergent compositions are:
a) surface-active agents, which can be anionic, nonionic, cationic or amphoteric in nature;
b) builders for detergency boosting and for binding the Ca/Mg hardness of the water;
c) enzymes, e.g. proteolytic, amylolytic, cellulolytic or lipolytic enzymes or mixtures thereof, particularly proteolytic and lipolytic enzymes;
d) bleaching agents for the removal of bleachable stains.
In addition, the detergent composition may also contain one or more of the following specific functional ingredients, though in small amounts, to give additional benefits for a top quality product, such as optical whitening agents, anti-redeposition agents, polycarboxylate polymers, stabilizers, anti-oxidants, foam-depressing agents, perfume, colouring agents and the like.
The bleach system as now used in concentrated and highly concentrated detergent powder formulations is still the same as that used in conventional powders and consists of a mixture of a peroxygen bleach compound, e.g. sodium perborate mono- or tetrahydrate, particularly the monohydrate, or sodium percarbonate, and a peroxyacid bleach precursor, e.g. tetraacetylethylene diamine (TAED).
Normally, the required level of sodium perborate or other peroxygen compound in such compositions will be from about 10 to 25% by weight, and the peroxyacid bleach precursor, e.g. TAED, is generally present at a level of from about 2 to 10% by weight, making up to a total level of bleach component of from about 12 to 35% by weight of the composition.
It is obvious that any means that could still reduce the pack volume, however small, without affecting the washing power, is most important.
In addition, with the trend towards still lower fabric washing temperatures to e.g. 40.degree. C. and below, there is an incentive to constantly improve on the bleaching performance of TAED/peroxygen compound systems. One option is to replace TAED by a more reactive bleach precursor, though being a peroxyacid bleach precursor, the required level in the composition will still be in the order of about 2-10% by weight.
The present invention relates to the use of a metal-complex bleach catalyst in concentrated and super-concentrated detergent powder compositions.
In contrast to organic peroxyacid bleach precursors, which function by the mechanism of reacting with the peroxygen compound forming the corresponding peroxyacid, bleach catalysts work differently and are effective already in very small amounts.
Many transition and heavy metal complexes have been proposed as peroxide bleach catalysts, but they all suffer from one or more drawbacks for being of practical value, e.g. they are either environmentally less acceptable, of insufficient activity, or of insufficient stability.